Information recording method and apparatus

ABSTRACT

An information recording method for recording information on a rewritable recording medium include recording synchronizing signal information in a synchronizing signal portion on the rewritable recording medium, and recording data information in a data portion of the writable recording medium after the synchronizing signal portion by forming a record mark in the data portion. The data information corresponds to both ends of each record mark. Each time the synchronizing signal information is recorded, a length of the synchronizing signal portion changes and a start position of the synchronizing signal portion changes, and each time the data information is recorded, the record mark and space between the record mark are substantially inverted.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This is a continuation of U.S. application Ser. No. 09/949,640,filed Sep. 12, 2001, which is a continuation of U.S. application Ser.No. 09/712,969, filed Nov. 16, 2000, now U.S. Pat. No. 6,307,825, whichis a continuation of U.S. application Ser. No. 09/535,016, filed Mar.24, 2000, now U.S. Pat. No. 6,181,661, which is a continuation of U.S.application Ser. No. 09/350,282, filed Jul. 9, 1999, now U.S. Pat. No.6,104,692, which is a continuation of U.S. application Ser. No.08/863,126, filed May 27, 1997, now U.S. Pat. No. 5,953,299, the subjectmatter of which is incorporated by reference herein.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to a so-called mark-edge recordingin which marks are recorded in certain areas of a recording medium sothat their physical property is made different from the other areas tothereby have information associated with both ends of each of the marks.

[0003] The present invention is particularly suited to a rewritablehigh-density information recording method capable of recordinginformation to be repeatedly rewritable. The present invention is alsosuited to a so-called phase-changing type information recording methodin which the physical property of the information recorded areas is madedifferent from the other areas by the phase change of the recordedsubstance that is caused by changing the temperature of the informationrecording medium.

[0004] A conventional rewritable information recording method isdisclosed in, for example, JP-A-63-229625. This method is an opticaldisk recording method for recording information by modulating theintensity of light.

[0005] As shown in FIG. 6, information is recorded in a plurality ofsectors 21, each of which has identification information 24 provided atits head in order to indicate the physical position of information. Thisidentification information 24 is used as a reference to be followed by asynchronizing signal portion 22 and an information recorded portion 23which are recorded as a record unit on the recording medium. At thistime, the start position of the record unit is randomly changed in itsposition at each time of rewriting, thereby increasing the possiblenumber of times of repeated rewriting. In other words, the disk materialat the same place within a sector is prevented as much as possible frombeing deteriorated by repeated rewriting, thereby raising the possiblenumber of times of repeated writing.

[0006]FIG. 7 illustrates the relation between the number of times ofrewriting and the jitter in the case where the same recordinginformation is repeatedly recorded. Here, the jitter is defined as thestandard deviation normalized by a reproduction detection window width,the standard deviation being of the time shift between a reproductionclock and a reproduced data after the same random data is EFM-modulated,recorded repeatedly and then reproduced.

[0007] In FIG. 7, a curve 701 was obtained when the start position ofthe recorded portion is shifted by 2 bytes in the mark-edge recording, acurve 702 when shifted by 30 bytes in the mark-edge recording, a curve703 when shifted by 2 bytes in the mark-position recording, a curve 704when shifted by 100 bytes in the mark-edge recording, and a curve 705when shifted by 30 bytes in the mark-position recording. Here, themark-position recording is the recording system in which information isrecorded in association with the center position of the mark.

[0008] From FIG. 7, it will be seen that the increase of jitter afterrewriting can be suppressed more, or the possible number of times ofrewriting is increased as the amount of the shift of the start positionof the recorded area is increased. Here, the minimum mark distance, inthe mark-position recording in which data is associated with the centerposition of the mark, was selected to be 0.9 μm, and the minimum markdistance, in the mark-edge recording in which data is associated withboth ends of the mark, was chosen to be 0.6 μm. In addition, thediameter of the recording and reproducing spot was 0.9 μm, and therecording medium used was a GeSbTe-based phase-change recording medium.

[0009] However, in the start-position shift system, and particularly inthe mark-edge recording, the shift of the start position of the randomlyrecorded data must be increased to about 100 bytes in order to achieve apractical possible number of times of rewriting, as will be understoodfrom FIG. 7, when the same information is repeatedly rewritten.Therefore, the utilization efficiency of sectors was greatly reduced. Inaddition, under this great positional shift, the beginning end or lastend of recorded information will be superimposed upon other recordedportions. Since the recording characteristics of the beginning end orlast end of recorded information are deteriorated probably due to thedissolution or flow of the recorded film, the effect of the change ofthe recording and production characteristics may be expanded over a widerange by repeated rewriting of these portions.

SUMMARY OF THE INVENTION

[0010] It is an object of the present invention to provide aninformation recording method capable of greatly increasing the possiblenumber of times of repeated rewriting without reducing the recordingefficiency in a rewritable high-density information recording method forrepeatedly rewriting information so that the recorded information can beassociated with both ends of a mark.

[0011] It is another object of the invention to provide an informationrecording apparatus capable of greatly increasing the possible number oftimes of repeated rewriting without reducing the recording efficiency ina rewritable high-density information recording method for repeatedlyrewriting information so that the recorded information can be associatedwith both ends of a mark.

[0012] The present invention, in order to achieve the first object,provides the following aspects.

[0013] (1) An information recording method is provided for repeatedlyrecording information on a recording medium in association with bothends of each of marks that are formed to be different in their physicalproperty from other areas, wherein each time information is recorded,the marks and the spaces between the marks are substantially randomlyinverted in their positions.

[0014] Thereby, when repetitive rewriting is made, the total number oftimes that the marks and spaces are recorded is uniform over all themedium, and therefore the medium is physically uniformly changed byrepetitive recording. Accordingly, the possible number of times ofrepetitive rewriting can be greatly increased. This does not reduce theinformation recording efficiency at all.

[0015] (2) The substantially random inversion is made at each recordunit.

[0016] Here, the record unit is a unit such as a sector that is actuallyrecorded on the recording medium. In other words, any smaller ones thanthese record units are never rewritten as information on the recordingmedium. Of course, it is possible that after the record units arereproduced, only part of the reproduced information is modified andagain recorded as in the read-modify-write process so that the minimumunit to be recorded can be apparently reduced. However, even in thiscase, the above-given record units are actually recorded on andreproduced from the medium. If this inversion occurred within the recordunit, a complicated process would be necessary at the time of signalreproduction.

[0017] Thereby, the total number of times that marks are recorded ineach record unit is uniform over the record unit. Since the reproductionprocess is generally made for each information record unit, the changeof the medium due to repetitive recording of each record unit isuniform, and thus the possible number of times of repetitive rewritingcan be increased.

[0018] (3) An information recording method is provided for repeatedlyrecording information on a recording medium in association with bothends of each of marks that are formed to be different in their physicalproperty from other areas, wherein a synchronizing signal formed of aplurality of marks is provided at the head of an information recordedportion, and the number of marks of the synchronizing signal is changedeach time information is rewritten so that the length of thesynchronizing signal can be substantially randomly changed.

[0019] Thereby, since the region in which the synchronizing signal isrecorded is used as an adjustment region, the position of theinformation recorded portion is substantially randomly changed.Therefore, when repetitive rewriting is made, the total number of timesthat the marks and spaces are repeatedly recorded is uniform over allthe medium in each record unit. Consequently, the recording medium isuniformly changed in the physical property by the repetitive recordingwith the result that the possible number of times of repetitiverewriting can be greatly increased.

[0020] (4) An information recording method is provided for repeatedlyrecording information on a recording medium by forming recorded marksthat are different in their physical property from other areas so thatthe information corresponds to both ends of each of the marks, wherein asynchronizing signal having a plurality of marks and spaces is providedat the head of the information recorded portion, and each time theinformation is rewritten, the number of the marks or the spaces of thesynchronizing signal is changed so that the length of the synchronizingsignal is substantially randomly changed, and the marks and the spacesbetween the marks are substantially randomly reversed in theirpositions.

[0021] Thereby, when repetitive rewriting is made, the total number oftimes that the marks and spaces are repeatedly recorded is more uniformover the medium, and hence the possible number of times of repetitiverewriting can be more increased.

[0022] (5) The length of a guard portion which has dummy data and isprovided at the back end of the information recorded portion is changeddepending upon the length of the synchronizing signal portion.Therefore, the total length of the record unit ranging from the head ofthe synchronizing signal portion to the back end of the guard or dummydata portion is substantially unchanged.

[0023] Thereby, since the total length of the record unit issubstantially unchanged, the change of the beginning end and last end ofinformation does not affect the information recorded portion at thecenter of the information. Therefore, the possible number of times ofrepetitive rewriting can be suppressed from being reduced by the effectof the change of the beginning end and back end of information.

[0024] (6) Each time the information is rewritten, the informationrecording start position is substantially randomly changed.

[0025] Thereby, when repetitive rewriting is made, the total number oftimes that the marks and spaces are repeatedly recorded can be made moreuniform over the medium. Therefore, the possible number of times ofrepetitive rewriting can be more increased.

[0026] (7) An information recording method is featured in that thechange of the information recording start position is smaller than thatof the length of the synchronizing signal.

[0027] Thereby, the change of the beginning end and back end ofinformation does not affect the central portion of information, or theinformation recorded portion irrespective of the change of theinformation recording start position. Consequently, the possible numberof times of repetitive rewriting can be suppressed from being reduced bythe effect of the change of the beginning end and back end ofinformation. Therefore, the possible number of times of rewriting can begreatly increased.

[0028] The present invention, in order to achieve the second object,provides the following aspects.

[0029] (8) An information recording apparatus is provided for recordinginformation on a recording medium by a structure having at least arecord/reproduce head and a recording pulse generation circuit, furtherincluding at least a random signal generation circuit, a timinggeneration circuit, and any one of at least a polarity inverting circuitfor inverting the recording pulse polarity in accordance with a randomsignal generated from the random signal generation circuit, and asynchronizing signal generation circuit having a function to change thelength of the synchronizing signal.

[0030] Thus, since at least one of the polarity and timing of therecording pulse can be changed during recording, the total number oftimes that the marks and spaces are repeatedly recorded when repetitiverewriting is made can be made uniform over the medium. Consequently, thepossible number of times of repetitive rewriting on the recording mediumcan be increased.

[0031] Here, the recording pulse is not any one of the pulses themselvesof heat, light and magnetic field to be applied to the medium at thetime recording on the medium. The actual pulse to be applied to themedium is formed after being converted by a recording pulse shapingcircuit or the like into a multi-pulse train or the like depending onthe characteristic of the medium, and then recorded.

[0032] (9) In addition, the recording pulse is passed through asynthesizing circuit after the generation of the synchronizing signal,coded data and dummy data, and then its polarity is inverted.

[0033] Thus, the polarity can be surely inverted without dependence onthe encoding circuit and system for recording.

[0034] (10) The polarity of the synchronizing signal generated from thesynchronizing signal generation circuit is at least changed inaccordance with the above-mentioned random signal.

[0035] Thus, since the polarity of the recording pulse can beautomatically inverted without additionally providing a polarityinverting circuit, the apparatus can be fabricated at low cost.

[0036] As described above, according to the present invention, there isprovided an information recording method for recording information onthe medium in a form of an array of recorded marks so that the “0”s or“1”s of binary information are made associated with both ends of each ofthe recorded marks, and featured in that if the same information isrecorded a plurality of times, an array of recorded marks recorded onthe medium according to the information includes an array in which therecorded marks and the spaces between the marks are inverted in theirpositions. Therefore, even though the same information is repeatedlyrecorded on the medium, the marks are not formed at a particularlocation, but can be uniformly formed over the medium by an energy beam,and thus the life of the recording medium can be expanded.

[0037] Moreover, the recording medium of the invention has formed alongtracks a plurality of sectors each of which has a data region in whichthe recording data is recorded, a synchronizing signal region providedbefore the data region, and a dummy data region provided after the dataregion, the length of the synchronizing signal region included withineach sector being not constant, the length of the range from the head ofthe synchronizing signal region to the back end of the dummy data regionbeing constant.

[0038] Furthermore, a preferred embodiment of the medium has formedalong tracks a plurality of sectors each of which has a data region inwhich the recording data is recorded, first and second regions providedbefore and after the data region, and an identification informationportion provided before the first region, the length of the first regionwithin each sector being not constant, the length of the range from thehead of the first region to the back end of the second region beingconstant, the distance from the head of the first region to the back endof the identification information portion being not constant.

[0039] Thus, the recording medium is deteriorated uniformly by theirradiation of energy beam, and hence high reliability can be ensured.

BRIEF DESCRIPTION OF THE DRAWINGS

[0040]FIGS. 1A and 1B are a conceptional diagram and a pulse waveformdiagram for explaining one embodiment of an information recording methodof the present invention;

[0041]FIG. 2 is a plan view showing another embodiment of theinformation recording method of the present invention;

[0042]FIG. 3 is a plan view showing still another embodiment of theinformation recording method of the present invention;

[0043]FIG. 4 is a plan view of showing a further embodiment of theinformation recording method of the present invention;

[0044]FIG. 5 is a block diagram of an information recording apparatusshowing an embodiment of the present invention;

[0045]FIG. 6 is a plan view of for explaining one example of the priorart information recording method;

[0046]FIG. 7 is a graph showing the effect and drawbacks of the priorart information recording method;

[0047]FIG. 8 is a graph showing the effect of the information recordingmethod according to the present invention; and

[0048]FIG. 9 is a circuit block diagram of part of the informationrecording apparatus according to the embodiment the present invention inconjunction with FIG. 5.

[0049] Other objects, features and advantages of the present inventionwill become apparent from reading of the following description ofembodiments of the invention in conjunction with the accompanyingdrawings. Like reference numerals and symbols indicate like elements,parts or circuits in the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] Embodiments of the invention will now be described in detail withreference to the drawings.

[0051] (Embodiment 1)

[0052]FIG. 5 shows an information recording apparatus of an embodimentof the invention. This apparatus includes a record/reproduce head 32irradiating to a recording medium 8 an energy beam that is based on arecording pulse corresponding to coded recording data of binaryinformation, to form recorded marks on the medium. The “1”s or “0”s ofthe binary information are recorded corresponding to the edges of therecorded marks. This apparatus also includes a pulse conversion circuit34 for reversing the polarity of the recording pulse. Thepolarity-reversed recording pulse may be a pulse of which the leadingedges and trailing edges correspond to either “1”s or “0”s of the binaryinformation. In this embodiment, a phase-change type optical recordingmedium (recording film: GeSbTe based material) is used as the recordingmedium. Therefore, the laser beam is modulated in its intensity, andirradiated on the recording medium to form recorded marks as amorphousportions within a crystal region of the medium.

[0053] Referring to FIG. 5, there are shown the record/reproduce head 32which records and/or reproduces on the recording medium 8, a detectioncircuit 33 which detects the reproduced signal from the record/reproducehead 32, and a reproduction circuit 41 which reproduces information fromthe detected signal. The reproduction circuit 41 has at least anidentification information detection circuit 42 which detectsidentification information on the medium. The identification informationsignal from the identification information detection circuit 42 issupplied to a timing generation circuit 40, which then generates variousdifferent timing signals for the recording operations.

[0054] The apparatus of this embodiment also includes at least a randomsignal generation circuit 36. The random signal generation circuit 36may include a quasi-random sequence generator or may generate a randomsignal from the information asynchronous with the recording andreproduction operations, such as time or date. The apparatus of thisembodiment further includes an encoding circuit 38 which encodesrecording information (recording data) 50. This encoding circuit 38 isnot necessarily provided within the apparatus depending on the recordingcode.

[0055] This embodiment employs (2, 11) RLL coding. A synthesizingcircuit 35 provided in the apparatus combines the synchronizing signalfrom a synchronizing signal generation circuit 37, the coded data fromthe encoding circuit 38, and the dummy data from a dummy data generationcircuit 39 in accordance with a timing signal from the timing signalgeneration circuit 40, to generate coded composite data 51 that is to berecorded as recorded units. The pulse conversion circuit 34 converts thecoded composite data 51 into a recording pulse 53 with the polaritydepending on the random signal 52 produced from the random signalgeneration circuit 36. In this case, the polarity inversion according tothe random signal 52 is made for each record unit. The polarityinversion timing is controlled by a timing signal 54 from the timinggeneration circuit. The recording pulse thus generated is fed to arecording pulse shaping circuit 31 by which it is converted into a pulseform suitable for the record/reproduce head and the recording medium.The shaped pulse is supplied to the record/reproduce head 32 by whichthe energy beam according to this pulse is applied to the recordingmedium 8 to form recorded marks on the medium.

[0056] With reference to FIGS. 1A and 1B, a description will be made ofthe relation between the finally recorded marks and the coded data inthis embodiment.

[0057] Referring to FIG. 1A, a coded data sequence“0010000100100001000100” is converted in NRZI-NRZ scheme into arecording pulse of a form A: “001111100011111000011” or B:“1100000111000001111000”, by the pulse conversion circuit 34.

[0058] The coded data sequence is, for example, a pulse 51 having highlevels at “1”s as shown in FIG. 1B. The pulse conversion circuitconverts this pulse 51 into a pulse 53A or a pulse 53B with the polarityopposite to the pulse 53A.

[0059] When the recording pulse 53 is shaped into a multi-pulse train bythe recording pulse shaping circuit 31, and then recorded on the medium,a mark 6 associated with the “1”s of the recording pulse and a space 7corresponding to the “0”s are formed on the recording medium asillustrated in FIG. 1A. In other words, the mark 6 and the space 7between the marks 6 in the recording pulse A are respectively turnedover in the pulse B to be the space 7 and the mark 6, associated with“0”s and “1”s. Thus, there is no problem in the reproduction even whenthe mark and space are turned over, respectively. This is because thereproduced data from A and B are the same coded data since the signalcorresponding to both ends of the recorded mark 6, or the boundarybetween the mark 6 and the space 7 is detected at the time ofreproduction.

[0060]FIG. 9 shows one example of the pulse conversion circuit 34 inthis embodiment. When a timing signal 54 is turned to be at a logicalhigh level, the binary random signal 52 is selected as an initial valueinto one input of an exclusive logic sum circuit EX-OR to the otherinput of which the coded composite data 51 is applied. Then, when thetiming signal 54 is turned to be at a logical low level, the exclusivelogic sum circuit EX-OR produces the recording pulse signal 53A or 53B,or an exclusive logic sum of the output from the exclusive logic sumcircuit EX-OR and the coded composite data including the coded datasequence 51.

[0061] In this embodiment, the beginning end of the record mark israndomly shifted in addition to the inversion of polarity. This randomshift timing control is made by controlling the output timing of thesynthesizing circuit 35 under the timing generation circuit 40. Thetiming generation circuit 40 randomly shifts the recording start timingin accordance with the signal from the random signal generation circuit36.

[0062]FIG. 8 shows jitter characteristics obtained when the same data isrepeatedly recorded on one recording medium according to thisembodiment. In FIG. 8, a curve 81 was obtained when the recording startposition was shifted by two bytes, but when there was no polarityinversion. A curve 82 was obtained when the recording start position wassimilarly shifted by two bytes and when polarity inversion was made. Inthis case, the standard deviation of the time shift between thereproduction clock and the reproduced data after the same data wasrecorded repeatedly and then reproduced was normalized by thereproduction detection window width and used as the rate of jitter. FromFIG. 8, it will be obvious that even when the recording start positionis shifted by a small value in the order of two bytes, the possiblenumber of times of rewriting can be increased much more by theadditional polarity inversion in this embodiment than in theconventional apparatus (with no polarity inversion). In this experimentfor the jitter characteristic, the minimum mark length was selected tobe 0.6 μm, and the record/reproduce spot diameter was 0.9 μm.

[0063] According to this embodiment, as described above, the marks 6having the first optical property and the spaces 7 having the secondoptical property are formed on the recording medium, and informationassociated with a binary code of “1”s or “0”s is recorded as anexistence of boundary between a mark and a space. In this recordingmethod, even if the same information is recorded a plurality of times,both cases in which the boundary corresponding to a particular binarycode of information is changed from mark to space and changed from spaceto mark are controlled so as to appear in a plurality of repeatedrecording operations. Thus, the reliability in the recording medium canbe increased.

[0064] (Embodiment 2)

[0065] Another embodiment of the invention will be described. Theinformation recording apparatus of this embodiment is the same as inFIG. 5. In other words, this apparatus has the record/reproduce head 32for recording and/or reproducing on the recording medium 8. Thereproduced signal from the record/reproduce head 32 is detected by thedetection circuit 33, and the detected signal is fed to the reproductioncircuit 41 by which information is reproduced from the detected signal.The reproduction circuit 41 includes at least the identificationinformation detection circuit 42 for detecting the identificationinformation on the medium. The identification information signal fromthe identification information detection circuit 42 controls the timinggeneration circuit 40 to generate various different timing signals forthe recording operations. The apparatus of this embodiment also has atleast the random signal generation circuit 36. The random signalgeneration circuit 36 may include the quasi-random sequence generator,or may generate the random signal from the information asynchronous tothe recording and reproduction operations, such as time or date.

[0066] The apparatus of this embodiment further has the encoding circuit38 which encodes recording information (recording data) 50. Thisencoding circuit 38 is not necessarily provided within the apparatusdepending on the recording code.

[0067] This embodiment employs (2, 11) RLL coding. The synthesizingcircuit 35 provided in the apparatus combines the synchronizing signalfrom the synchronizing signal generation circuit 37, the coded data fromthe encoding circuit 38, and the dummy data from the dummy datageneration circuit 39 in accordance with the timing signal from thetiming signal generation circuit 40, to generate the coded compositedata 51 that is to be recorded as recorded units. The synchronizingsignal generation circuit changes the length of the synchronizing signalin accordance with the random signal generated from the random signalgeneration circuit 36. The dummy data generation circuit changes thelength of the dummy data in accordance with the random signal generatedfrom the random signal generation circuit 36. The pulse conversioncircuit 34 converts the coded composite data 51 into the recording pulse53 of a particular polarity. In other words, such polarity inversion asin the previous embodiment is not made. Thus, the generated pulse isconverted into a pulse suitable for the actual record/reproduce head andrecording medium by the recording pulse shaping circuit 31, and therecord/reproduce head 32 applites the energy beam according to theshaped pulse on the recording medium 8 to form the recorded marks on themedium.

[0068] In this embodiment, the recording information is recorded to bearranged on the recording medium as illustrated in FIG. 2. In otherwords, the synchronizing signal portion 22 which may be considered as aguard portion is placed at a position separated about a certain distancefrom the identification information 24 that indicates the head of thesector 21, and the length of the synchronizing signal portion 22 ischanged at each sector 21. The synchronizing signal portion 22 isfollowed by the information recorded portion 23 and the guard portion 25in this order. The length of the synchronizing signal portion is changedin accordance with the random signal generated from the random signalgeneration circuit 36. The length of the dummy data is changed by thedummy data generation circuit 39 in accordance with the random signalgenerated from the random signal generation circuit 36. At this time,the distance from the head of the synchronizing signal to the back endof the guard portion is kept substantially constant.

[0069] Thus, even if the data in the information recorded portion is thesame as in the previous recording, the information recorded portion 23can be moved back and forth so that the position of the informationrecorded portion 23 on the medium is randomly changed. As a result, thetotal number of times of recording marks and spaces is kept uniform overall positions on the recording medium. Thus, the change of the recordingmedium due to the repeated recording can be averaged so that thepossible number of times of repeated rewriting can be increasedsimilarly to the prior art that is the mark position recording, althoughthis embodiment is the mark-edge recording. In this case, since therecording start position and recording end position are respectivelymaintained to be substantially unchanged unlike the operation of theconventional apparatus. Therefore, even if the amount of shift of theinformation recorded portion 23 is selected to be about 30 to 100 bytes,the change of the recording and reproduction characteristic of themedium at around the recording start point and recording end point doesnot affect the recorded portion. Accordingly, the information recordedportion 23 can be easily shifted by a large amount, thus making itpossible to increase the possible number of times of rewriting.

[0070] According to this embodiment, there is provided an informationrecording method in which a record mark is formed in the data region ofthe recording medium, and information is recorded in association withboth ends of the record mark, as described above. In this method, firstand second adjustment regions are provided at the front and back ends ofthe data region, and changed in their lengths so that the data region isshifted in its position. In addition, when the same information isrecorded a plurality of times, the arrays of a plurality of record marksformed on the recording medium in association with the same informationinclude opposite arrays in which the record marks and the spaces betweenthe record marks are inverted as opposed to the former arrays.

[0071] (Embodiment 3)

[0072] This embodiment employs the same apparatus as Embodiment 2. Thelength of the synchronizing information is changed. In this case, thesynchronizing information includes a first synchronizing informationportion 221 (VFO) that has marks 6 and spaces 7 of the same lengthalternately and repeatedly arranged in turn, and the length of thesynchronizing information portion 221 and its polarity at the end arechanged. Specifically, the polarity is automatically changed dependingon whether the total number of marks and spaces is even or odd. Inaddition, a second synchronizing information portion 222 (SYNC) isprovided to follow the first synchronizing information portion 221. Thissecond synchronizing information portion 222 has a fixed pattern, butits polarity is changed depending on the polarity of the final end ofthe first synchronizing information portion 221.

[0073]FIG. 3 shows examples (A), (B) of the first synchronizinginformation portion 221 in which the total number of marks and spaces isodd, and an example (C) of the first synchronizing information portion221 in which the total number of marks and spaces is even.

[0074] Since this embodiment is capable of making polarity inversionwithout any polarity inverting circuit, the recording apparatus issimple in construction. In addition, since the information recordedportion 23 can be shifted in its position, the accumulated number oftimes that the marks and spaces are recorded is more uniform over therecording medium. Thus, the medium is more uniformly changed by repeatedrecording with the result that the possible number of times of repeatedrewriting can be increased more than in Embodiment 1.

[0075] (Embodiment 4)

[0076] This embodiment employs the same apparatus as Embodiment 3. Asshown in FIG. 4, the length of the first synchronizing informationportion 221 is randomly changed, and also the recording start positionof the first synchronizing information portion 221 is changed inaccordance with the random signal. The amount of shift of the recordingstart position is substantially equal to the length of the marks (˜¼byte) within the first synchronizing information portion 221. Thus,since the total number of times at which the marks and spaces within thesynchronizing information portion are recorded is uniform over all themedium, the possible number of times of repeated rewriting is increasedmore than in Embodiment 3. In addition, since the amount of shift of therecording start position is small enough, the recording start positioncan be considered not to be changed from the standpoint of the change ofrecording and reproduction characteristics at around the recording startposition. Thus, there is no adverse effect of shift which appears in theprior art.

[0077] Since the marks and spaces are repeatedly recorded while they areturned over at each repetition, the total number of times by which themarks and spaces are repeatedly recorded, or rewritten is uniform overall the recording medium. Thus, the recording medium is uniformlychanged by repetitive recording so that the possible number of times ofrepeated rewriting can be greatly increased. This does not reduce theinformation recording efficiency at all. In addition, since the positionof the information recorded portion on the medium is randomly changedwhen the length of the synchronizing signal portion at the head of theinformation recorded portion is randomly changed, the total number oftimes by which the Since the marks and spaces are repeatedly recordedwhile they are turned over at each repetition, the total number of timesby which the marks and spaces are repeatedly recorded, or rewritten isuniform over all the recording medium. Thus, the recording medium isuniformly changed by repetitive recording so that the possible number oftimes of repeated rewriting can be greatly increased. This does notreduce the information recording efficiency at all. In addition, sincethe position of the information recorded portion on the medium israndomly changed when the length of the synchronizing signal portion atthe head of the information recorded portion is randomly changed, thetotal number of times by which the marks and spaces are repeatedlyrecorded is uniform over all the medium. Therefore, the recording mediumis uniformly changed by repetitive recording, and hence the possiblenumber of times of repetitive rewriting can be increased.

1. An information recording method for recording information on arewritable recording medium comprising the steps of: recordingsynchronizing signal information in a synchronizing signal portion onthe rewritable recording medium; recording data information in a dataportion of the writable recording medium after the synchronizing signalportion by forming a record mark in the data portion, wherein said datainformation correspond to both ends of each record mark; wherein eachtime the synchronizing signal information is recorded, a length of thesynchronizing signal portion changes and a start position of thesynchronizing signal portion changes, and wherein each time the datainformation is recorded, the record mark and space between the recordmark are substantially inverted.
 2. An information recording methodaccording to claim 1, wherein the change of said information recordingstart position is smaller than that of the length of the synchronizingsignal portion.